Indicate the size (in arcsec) of a cross to be drawn at the map projection center, as a reference marker for relative positions. If 0, no cross is drawn.
If CROSS is non 0 and a script "my_cross.ima" is in the current
directory, this script is executed instead of drawing a simple cross.
This allows to display for example minor and major axes of inclined disks.
A generic example of such a script is available in
gag_demo:my_cross.ima
It can be tailored by controlling the variables in the mycross% structure.